The present invention relates to a scroll fluid machine and especially to a scroll fluid machine such as a scroll compressor or a scroll vacuum pump in which a fixed wrap of a fixed scroll engages with an orbiting wrap of an orbiting scroll mounted around an eccentric axial portion of a driving shaft, the orbiting scroll being eccentrically revolved by the driving shaft so that a gas sucked from the outer circumference of the fixed scroll can be compressed towards the center and discharged.
In a scroll fluid machine, a long-time operation increases temperature of an eccentric axial portion of a driving shaft, and bearings and packing that support the driving shaft to cause the bearings and packing to be damaged.
To prevent such situation, US2004/0241030A1 discloses a scroll fluid machine having a number of cooling fins on the surface of a fixed scroll to increase cooling efficiency.
However, in the scroll fluid machine, the cooling fins are radially provided on the surface of a fixed scroll to limit a cooling area and cooling performance. To increase the cooling area, increased number of the radial cooling fins makes gaps between the cooling fins denser to make cooling wind more unlikely to pass through to decrease cooling efficiency. Particularly, in the radial cooling fins, the gap between the cooling fins becomes narrower towards the center to make it more difficult for cooling wind to pass through towards the center having relatively higher temperature than in the outer circumference.